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BSMS 103 > Theme 3 - ECG > Flashcards

Theme 3 - ECG Flashcards

1
Q

what type of junctions allow electrical coupling of cells?

A

gap junctions

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2
Q

what is the most numerous cell type in the heart?

A

contractile cells

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3
Q

what is the function of the fibrous skeleton?

A

electrically isolates the A from V so they don’t contract at the same time

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4
Q

how are cardiomyocytes linked?

A

by gap junctions at intercalated disks

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5
Q

what speed to A and V myocytes propagate at?

A

0.3-0.5m/s

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6
Q

what speed do modified myocytes in the purkinje fibres propogate at?

A

5m/s

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7
Q

what three things are intercalated disks made up of?

A

fascia adherens, gap junctions and desmosomes

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8
Q

what allows synchronous conduction of impulses from SA to AV node?

A

internodal bundles

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9
Q

how many specialised bundles are there in the atria and what do they contain?

A

four bundles that contain purkinje like cells

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10
Q

where is Bachman’s bundle found?

A

inner wall of the LA

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11
Q

what is the speed of transmission at the AV node and why?

A

slow to allow atria to empty blood into the ventricles so that they are full at systole

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12
Q

what sequence does depolarisation pass in the ventricular wall?

A

septum then apex then AV groove

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13
Q

what does an ECG show?

A

individual currents of cardiomyocytes that work together in a functional syncytium

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14
Q

what is an ECG lead and where is it connected?

A

a configuration of electrodes - positive (ankle or leg), negative (wrist) and sometimes a ground electrode

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15
Q

how many electrodes does a 12 lead ECG use?

A

10

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16
Q

what type of leads make up 12 standard lead ECG?

A

3 bipolar leads (frontal plane), 3 augmented leads (coronal plane) and 6 pre cordial leads (thorax near the heart)

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17
Q

what does the P wave represent?

A

depolarisation in atria from SA node

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18
Q

what does the PR segment represent?

A

SA to AV delat to allow ventricular filling

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19
Q

what does QRS represent?

A

movement of electrical activity through the ventricles (both ventricles need to be simultaneously depolarisation)

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20
Q

what does ST represent?

A

beginning of ventricular repol (should be flat)

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21
Q

what is the T wave?

A

ventricular repolarisaton

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22
Q

what are escape beats and what do they appear as on ECG?

A

when ventricles dont get a signal so signals itself and the myocardium beats ineffectively (misshaped QRS)

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23
Q

what is a possible cause of wide QRS?

A

problems in the purkinje system

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24
Q

what is a large/deep Q wave a sign of?

A

dead tissue - old MI

25
Q

what is sinus tachycardia?

A

fast heart rate due to SA node beating too quickly

26
Q

how is atrial rate calculated?

A

P to P wave

27
Q

how is ventricular rate calculated?

A

RR interval (QRS to QRS)

28
Q

how can rate be calculated using boxes on ECG?

A

this is ventricular rate so counting how many big boxes occur between two R waves then 300/big boxes

29
Q

what are the names of pre cordial leads and what plane do they record from?

A

transverse - V1-V6

30
Q

what is the main NT in psym control of the heart and what receptors does it work on?

A

vagal drive from Ash which stimulates muscarinic receptors

31
Q

what drug is a muscarinic antagonist and therefore increases heart rate?

A

atropine

32
Q

is heart vasculature innervated by the psym system?

A

no

33
Q

what type of nerves does symp autonomic control work on?

A

stellate nerves

34
Q

what is the effect of a beta agonist on heart rate and what receptors does it work on?

A

increases rate via b2 adrenergic receptors

35
Q

what is the effect of beta blockers on heart rate and what receptors does it block?

A

decreases rate via adrenergic receptors

36
Q

what is AV block?

A

a delay due to failure of atrial signal to stimulate ventricles

37
Q

what three main things is AV block caused by

A
  • ischaemia of AV node or AV bundles - POOR PERFUSION
  • compression of AV bundle by scar/calcified tissue
  • inflammation of AV node or bundle
38
Q

what are the symptoms of AV block?

A

palpitations, hypotension like - dizziness, malaise, syncope and risk of sudden death
- patient can be asymptomatic

39
Q

How is 1st degree heart block characterised on ECG?

A

increased PR interval (more than 5 small boxes) but all Ps are followed by QRS

40
Q

what is first degree heart block usually due to?

A

delayed AV node transmission

41
Q

how is Mobitz type I 2nd degree heart block characterised on ECG?

A
  • some P waves are blocked and not followed by QRS

- some missing QRS (P wave gets longer until QRS fails to follow it - wenckebach)

42
Q

what is the cause of mobitz type I 2nd degree heart block and what treatment is usually given?

A

AV node damage and usually no treatment

43
Q

what are the two types of second degree heart block?

A

mobitz type I and II

44
Q

how is Mobitz type II 2nd degree heart block characterised on ECG?

A

consistent PR interval and some P waves blocked/not followed by QRS

45
Q

what causes Mobitz type II second degree heart block?

A

problems with ventricles or bundle of his

46
Q

is mobitz type II 2nd degree heart block high risk and what is the treatment?

A

yes it is high risk and treated by implanting a pacemaker

47
Q

how is 3rd degree heart block characterised on ECG?

A

distance of P to QRS is unrelated and PR interval varies radically

48
Q

what causes 3rd degree heart block?

A

AV node isn’t conducting so ventricles do their own thing (ectopic complex)

49
Q

what are they features of ventricular rate and atrial beats in 3rd degree heart block?

A

ventricular rate and atrial beats are consistent

50
Q

what is a premature beat?

A

early neats that can be triggered by irritable tissue

51
Q

what are escape beats and what triggers them?

A

late beats when the atrial signal is delayed or prevented that are triggered by natural rhythmicity of non atrial tissue

52
Q

what is the purpose of escape beats?

A

an extra beat to escape arrhythmia

53
Q

How is a premature ventricular contraction characterised on ECG?

A

Very wide QRS and no T wave, no S wave

- negative dip where T wave should be

54
Q

where are premature ventricular contractions often triggered and what does this result in?

A

in the middle of the myocardium (non purkinje)

- results in electrical unsynchrony, delayed and insufficient conduction

55
Q

what is atrial fibrillation and what happens?

A

disorganised electrical activity in the atria

- ventricular rate is faster and irregular as many signals reach the AV node but only some are transmitted

56
Q

how is atrial fibrillation characterised on ECG?

A

No P wave - flat or wiggly line instead

57
Q

what can AF lead to?

A

thrombus formation in the atrium due to slow flow of blood

- increased risk of stroke

58
Q

what is respiratory sinus arrhythmia?

A

heart beat is slight fasting during inspiration and slightly slower during expiration

59
Q

what is respiratory sinus arrhythmia a sign of and who is it most commonly seen in?

A

a healthy heart mostly seen in children and athletes

BSMS 103 (23 decks)

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